[jillesvangurp]

That's the excuse. Basically the real reason is that they only care about safety of the planes, not of the people handling the fuel (e.g. pilots, ground staff), or breathing the toxic fumes (everybody on or near an airport). So, they only care about safety when it is a very narrowly scoped notion of that concept.

Bureaucracies are weird like that. This is fundamentally not about people's safety but about covering their own safety (i.e. ass coverage). The problem is not something bad might happen but that they'd be held accountable for it.

Never mind that something bad has been known to happen for the last half century or so that they are not being held accountable for. People actually get sick and die because of leaded fuel but it's not their problem. And never mind that the bad thing that might happen is basically some ancient engines not running that well with unleaded fuel. That's why certification processes exist for engines. You can test this and decide to not certify certain engines for unleaded fuel. Ensuring people fly around with certified engines definitely is their problem. Any modern engine is basically certified for unleaded fuel already.

[M3L0NM4N]

I mean, planes falling out of the sky is a fairly significant safety issue. "Safety of the plane" is misleading if there's people inside the planes lol.